That border you either pay and walk straight back into Thailand or proceed to Malaysia and you may have to stay 1 night. For me 2000b has only gone up slightly over the years.
You can do your re entry at the immigration office in Nongkai and not at the border. Exit the train at Nongkai station and get a tuk tuk to the immigration office then proceed to the border. Remember alot of the immigration offices maybe closed until the New Year
recently returned from overseas and had online 90 day rejected. The AI program is fussy, so just went to immi office and 5 minutes later walked out all done , no questions. Enjoy Thailand
Go to the immigration office near the airport in NST and fill in the form and pay your money. I usually copy every page with stamps on it in your passport. There is no public transport to this office so you may need a Grab or motorbike to take you there.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.