I went to Cambodia to get my 90 day visa and when I was coming back into Thailand I was only stamped for two weeks.. I just now noticed this and it's been more than two weeks now, what should I do?

Go to your nearest immigration office. It was a mistake and they should be able to correct it for you.

"I went to Cambodia to get my 90 day visa and when I was coming back into Thailand I was only stamped for two weeks.. I just now noticed this and it's been more than two weeks now, what should I do?"

Details on the "90 day visa" you went to get would be helpful. Also, if you are talking about exit/re-entry on a double or multiple tourist visa, check the expiration date in your passport. If you exited the kingdom after the expiration date you've lost it and the 15 entry permit is correct.

What visa did you obtain in Cambodia and where? You do not obtain a visa crossing the border so unless you had a multi entry visa that was valid you would only obtain 15 days if from most visa exempt countries.

What visa did you obtain in Cambodia and where? You do not obtain a visa crossing the border so unless you had a multi entry visa that was valid you would only obtain 15 days if from most visa exempt countries.

I obtained a two entry tourist visa in Phnom Penh.

What visa did you obtain in Cambodia and where? You do not obtain a visa crossing the border so unless you had a multi entry visa that was valid you would only obtain 15 days if from most visa exempt countries.

I obtained a two entry tourist visa in Phnom Penh.

Go to immigrations and get it corrected.

Check your stamps always before leaving.

How much longer than two weeks ago? AFAIK PP has not been providing such visas for some time now so have you checked your passport and sure it actually is in there? If it is immigration apparently did not see and just provided a visa exempt entry. Bangkok Immigration office at Chiang Wattana can correct this.