Sounds good in principle, but learning to speak all SE Asian languages would require you to be some kind of linguistic genius and probably half a lifetime of devotion. Speaking only one of the languages from the region, say Thai or Burmese or Vietnamese, wouldn't help much in neighboring countries since each language in the region is not mutually intelligible with only limited overlapping...so such an approach would mean limiting your engagement to one country.

In parts of northern Laos and northern Myanmar, no attempts are made by Chinese settlers to learn the local language - everything (signboards, menus etc.) is in Chinese and locals [Laotians and Burmese] who can't speak this foreign language [Chinese] are left out.

Also, I don't think English should be forgotten - despite various levels of English fluency in the region, English is still the only global lingua franca and the global language of business. English is the only language you can successfully use in all SE Asian countries. While it's great to know Thai, Lao, Burmese etc. it isn't realistic unless you are living in those countries. I have also noticed that just like with English, Chinese learners of these SE Asian languages really struggle, and when encountering a local that speaks good English, the conversation will usually inevitably switch to English since the local will assume the other party can't speak their language well enough. It's only once fluency is achieved that this is overcome.

My recommendation would be for both Chinese and other foreigners interested in investing/doing business with the region to know how to speak English fluently, followed by becoming proficient in at least the basics of their host countries' language to at least show some interest and respect. Apart from those interested in becoming translators however, I personally think time and money is better spent gaining technical skills and then applying some language skills on the side - not the other way round.

I've done that and I'm doing quite well. I am an engineer that has worked in Vietnam and Thailand and I speak Thai and some Lao with an almost native accent (and can read and write both languages) - something that is of enormous benefit to me, but I have achieved this as a side passion rather than as my main job. Still, I barely speak Vietnamese and don't have the energy or time to work on it - in any case, doing business isn't difficult as most educated people there speak English anyway and I have a very good friend who helps me so it's all good. Ditto for Cambodia and Myanmar.

I'm not as pessimistic as Yuanyangren. I know a fair amount of South-East-Asian students here in Kunming who, besides their own language and pretty good English, also speak Chinese and another South-East-Asian language.

When in Vietnam I heard a fair deal of Chinese, Lao and Cambodian. In eastern Thailand and southern Laos, a fair number of people could speak Vietnamese. People in eastern Burma were often also fluent in Thai as they often (illegally) cross the border to work in Thailand.

There are different reasons for this. First, culturally: except for Chinese, no language or nation is so much bigger than the other that it is not necessary for them to learn their neighbour's language (i.e. you don't have the France or Germany effect). Plus the fact that each country has a lot of immigrants and trade from neighbouring countries.

Linguistically: all of those languages are linguistically closer to each other than each of them is to English (tones, structure over flection, sounds ...), which makes it much easier for the speaker of one SEA language to learn the other. Also, you can pretty much consider Lao and Thai as one language.

Finally, you don't really need to know each language. One will do. Being a linguist myself, I know that knowing a fourth or a fifth language doesn't help. No company ever seeks polyglots. Most would rather employ two persons with different language skills.

That said, I indeed know very few Chinese who master any of those languages. They suffer from the France syndrome where their language is so overwhelmingly big that they do not need to know any others. This could prove a great opportunity for South-East-Asians who do master more than one language, in addition to Chinese.

Haha, well I don't think I was that pessimistic, and I do agree with you on some of your points - although being quite knowledgeable about languages myself, there is more overlapping of the dominant language from the more economically powerful country into the less dominant one than the other way round - i.e. despite what you said, there is very little Lao spoken in Vietnam, but the other way round there is quite a bit of Vietnamese understood in Laos. Lao officials on the Lao-Viet border can usually speak some Vietnamese, but Viet officials generally can't speak Lao. I have been there and know this for a fact. Same with Viet officials on the Chinese border - they can speak Chinese, but Chinese officials speak only Chinese and English, not Viet.

Vietnamese is also only understood amongst a very small minority of people on the Thai side of the Lao border, not many as you say...same with Thai in Myanmar but not Burmese in Thailand (except amongst the immigrant workers and some Burmese signboards near the Burmese border) in Thailand. As mentioned above, Chinese is quite strong in northern Laos, but Lao is non-existant anywhere in Chinese territory except when it comes to the Dai language, which is fairly close but not exactly the same language.

I've also found that the majority of South-East Asian Chinese language students here in Kunming don't speak much English at all for some strange reason. The ones back in their home countries that didn't major in Chinese are often quite good at English, so I guess there aren't that many polyglots around as you say - 2 languages seems to be what the average person knows and not more.

Although if we're on the subject of which SE Asian language to learn IN ADDITION TO English, which will continue to be important, then it must be Thai. Thai is understood throughout Thailand, Laos, western Cambodia and the Shan State of Myanmar. No other SE Asian language is as dominant as Thai.

This is reflected in the much greater interest amongst Chinese students in studying Thai than say, Vietnamese. I have met tons of Chinese students interested in, or with at least one semester of Thai behind them, but only two who had studied Vietnamese.

@bluppfisk, despite many SE Asian languages being more similar to each other than they are to English, this doesn't mean that say, a Chinese speaker will become more successful at learning Thai than they would be at English. When I was studying Chinese at YNNU and YU the Thai and Lao students in particular had great trouble with many of the sounds in Chinese, even if they had studied Chinese for a year or more, they still couldn't pronounce the "c" or "z" sounds correctly and they would always come out as sounding like an English "j" sound. For example, "baozi" would be pronounced by a Thai as "baojew".