Assuming you have a passport from one of the visa-exempt, or VoA countries, or have a valid visa, which covers your length of stay, you should be fine.

I guess if you want to be more comfortable, simply apply for a real double-entry Tourist Visa in your home country at the nearest Thai embassy/consulate

Asking the Thai "authorities" will result in a hundred different answers.

You could also ask here: http://www.thaivisa.com/forum/forum/...-work-permits/