If someone is serving a one-year ban from Thailand, can they travel to another Southeast Asian country during the ban, or is there some sort of agreement between the countries in that area, and in that case, they won't let you in? Thank you.

Common sense should tell you it's irrelevant for other countries

1 hour ago, Adrian78 said:

If someone is serving a one-year ban from Thailand, can they travel to another Southeast Asian country during the ban,

Yes

No problem at all traveling to any country other than Thailand.

I'm not even sure you can transit thru if you are on an overstay ban, so I wouldn't route any flights thru Thailand

I seem to recall that when traveling to Singapore one of the questions asked was around being denied entry to other countries so I asked Google if you could travel to Singapore whilst on a 1 year ban from Thailand and it's response was that it depends on the reason for your ban...

The Reason for Your Ban: If your Thai ban was related to a severe international issue, overstaying, or criminal activity, it could flag an alert during a Singapore border check. Singapore Immigration & Checkpoints Authority (ICA) officers reserve the right to deny entry if they deem a traveler inadmissible

I've had to look at this in the past (not for Thailand). I took a look and learnt that Thailand shares immigration intelligence with Cambodia, Laos, Vietnam & Myanmar. So, if you going to one of these expect issues.

Source - https://www.cmlocals.com/immigration/blacklist-status/

I've seen no evidence that your status would be shared with countries other than those, but it depends on the reason of course (e.g. Interpol Red Notice - although I doubt this is 'you').

I think it would depend on the reason for ban. If you were one of the idiots we read about they probably would deny. Over they probably will let you in

I’d check with the consulate, embassy or immigration direct to see what their response is. I wouldn’t give my name or details, but I’m sure they will want to know why you were banned in order to give you the correct information.

An obvious issue with Laos is that their officials can actually read the Thai-language ban and overstay stamps. If the one supposed to stamp you in sees that as a red flag, they could well decide not to take a gamble.

Seem to recall many years ago there used to be a question something along the lines of have you been refused entry to any country. That was in multiple countries not Thailand.

2 hours ago, emptypockets said:

Seem to recall many years ago there used to be a question something along the lines of have you been refused entry to any country. That was in multiple countries not Thailand.

I visit Vietnam often and need an eVisa. Oz pp

Never been asked that question