Hi, if I go to Thailand for 40 Days can I fly to Singapore for a week and still get back in to Thailand? I am US citizen.

I'm a us citizen flying into chiang mai. I'm staying 6 days and exiting the country into laos in chiang khong. A week later I'll be flying back to chiang mai from Cambodia with several hours until my flight back to the united states. I'll have to go thru customs/immigration to get my checked bag and then check it back in with the airline I'm flying home with.

So here's my question, will I have to pay the visa fee again since I have to go thru immigration or will they honor my previous stamp in my passport from the week before?

Also how much is the initial fee?

Thank you for your help!