Will I face immigration problems returning to Thailand after traveling to Vietnam and the Philippines?

No problem. If they question you, your pattern is reasonable. Have your exit ticket ready just in case.

So you been to Thailand with visa exempt 60+30=90? If your flying in? You be fine, but have a return ticket and cash for easiest entry.

Over 2 visa exempts and border bounces is when your on dodgy ground.

They want tourists not people with ties on business here.

As always the immigration officer stood in front of you will decide.

No

You should not have any problem at all with immigration based on the travel pattern you’ve described. You completed a full 60-day visa exemption, took a 30-day extension, and then left Thailand for more than four months while staying in Vietnam and the Philippines. That is a genuine and substantial absence, and it places you completely outside the scope of the new guidelines, which only target consecutive border bounces used to prolong a continuous stay. You have not overstayed, you have not tried to maximise back-to-back entries, and you have been out of Thailand far longer than the duration of your previous stay. In other words, you clearly fall into the category of a normal tourist. As always, the final decision rests with the immigration officer, but there is nothing in the current regulations or practice that suggests your entry would be problematic. Just make sure you carry an onward ticket within 60 days.

No you will have 60 days but if you want to extend you will be given 7 days - 2 exempt enterence a calender year one 30 day extension seems to be the going rate

Nobody knows but it sounds like normal tourist behaviour so probably not