Can I return to Thailand after a short trip to Cambodia or Malaysia if I've already extended my stay?

Why all the fear mongering?

Some people want to spend more than 90 days here. Maybe even 180. Taking time off from work, working remote, don’t plan to stay long enough to get a DTV.

Plenty of people spend half the year in one country. And half the year in the next.

Are you suggesting they should get a tourist visa for the second “90 days” ?

That’s reasonable. Just takes a little bit of planning. You’re not breaking any rules.

Have u asked a thai visa agent?

You’ll get another 60 plus you can extend but it’s up to the IO you stand in front of and many reports of people the extended being denied

Go spend a few weeks in the Philippines take your girlfriend I think you’ll have no problems and you get to live in a English speaking country for a few weeks

On re-entry you get another 60-day VISA EXEMPT but its up to the IO to let you enter. You may be questioned why so make sure you the 3 important requirements to enter.

If you get the 60 day visa exempt stamp and extend by a further 30 days at the Immigration office, Immigration class you as a tourist. If you then attempt to enter again on a visa exempt stamp, Immigration rightly consider that after on 90 day stay in the country that you are no longer a tourist but that you are attempting to live long term in the country. While there is no legal limit to the number of Visa exempt entries, once the Immigration officer believes that you are no longer visiting the country as a tourist he will deny you entry. If you have already stayed for 90 days on a visa exempt entry, then in future to guarantee entry into Thailand, you need to obtain a long term visa suitable to the reason for your stay.

Yes it's possible, but expect to be questioned upon re-entry. After you've spent 90 days in Thailand and then leave and return, they immediately know what you are doing (abusing the visa exempt system) and they no longer consider you a tourist. Your entry is at the discretion of the immigration officer.

Goggle it