Can I apply for a Thai eVisa while in Thailand and reenter with it?

You can try.

I applied and receive my eVisa from US, I was in the US but they didn't ask me where I was physically located and I doubt they check. You could use a VPN if you're overly concerned.

First congradulations for your successful arrival in Thailand. I saw your question in Vietnam Visa advice and it seems you've managed to make use of that ticket from US to Vietnam by transfering in HCMC to Thailand. You made it!

According to the official website of Thai e-visa, when we Chinese citizens apply for E-vsia, it is recommended that we submit the application to a Thai embassy/consulate which is in a country that:

1. you currently are

2. either your home country or a country where you have a residency.

In your case, you are currenly in Thailand, but your home country is China and you have residency in the USA.

So if you want to apply for an Evisa now in Thailand, you do not meet the requirement of this recommendation.

According to the official website of Thai e-visa, an alternative is that you can also submit the application to an embassy or consulate in the country where you currently are, but you are not a citizen of this country and you do not have residency in this country. However, the application process will take at least 30 days.

Unfortunately if you want to apply in Thailand you also do not meet the requirement of this alternative, because there is no Thai embassy/consulte in Thailand and you don't have 30 days.

So the safe way for you is definitely going back to the US and submit the Thai Evisa application there to a local Thai embassy/consulate.

However from what you wrote I think your plan is probably going to a nearby country instead of flying back to the US before you reenter Thailand.

Then you have two choices here:

1. Try to obtain a visa that is more than 30 days duration in that nearby country (like Cambodia or singapore) and upon your arrival, apply immediately for the Thai-evisa there to a Thai embassy/consulate in that country. You have to stay in that country for 30 days to wait for the E-visa.

顺便说一句，现在CCP把去过柬埔寨的人都当作潜在赌博电诈分子处理。

2. As some other people said, another method with considerable risk is to try your luck and submit your E-visa application to a Thai embassy/consulate in the US. You need to get a dummy flight ticket from the US to Thailand if you actually do not want to go back to the US. You have to gamble with the possibility that that consulate does not check whether you are currently in the US or not, because technically speaking you can only submit the application to a Thai embassy/consulate in the country where you currently are.

最后感叹下现在东南亚对我们中国国籍的人来说实在太不友好了。越南去不了，泰国也很难呆久。我也很快就只能回英国去了。因为我最近申请的两个泰国旅游签证间隔比较短，这次入境的时候被移民官警告啦。但是我真的只是在泰国吃喝玩乐啊。典型的游客，没有工作，没有做非法的事情😫唉。

Depends on which consulate you intend to use. Some may allow for that ( as in they may not check where you physically are). Many local SE Asia consulates are still using the manual apply in person and get a sticker in your passport.