Hello I am in samui now currently. I want to go Bangkok and fly back to my home country. I bought ticket from samui bkk for 06 April and for 07 April to bkk to turkey. but Thailand cancelled all flights until 09 April. I talked with Qatar airlines and they told me best possible flight is on 09 April. 
And samui will be closed after 07 April , no more flight and ferry after 07 April. Therefore I want to fly from samui in last day , 06 April. I will stay in Bangkok , at a hotel near airport and will not go outside. 
I read police put farang a quarantine in Bangkok. They can put me to quarantine too ? I live in samui for last 2 months. I will go out from hotel to go airport after 2 days , 09 April.  Do you think I will be put in quarantine in Bangkok ?

 

and another thing is after 08 April , airport will be open again ?

I suggest you follow this guy on Twitter.

He has excellent and up to date information for foreigners in Thailand in general and especially for people in your situation.

https://twitter.com/RichardBarrow/