Apologies if this is the wrong forum.

 

But can I fly from Suvarnabhumi to Ubon Ratchathani without quarantine.

Plan to book a ticket with Vietjet. 

 

Thanks in advance.

Officially (whether it is actually implemented is another thing), the latest TAT release dated Feb 03, 2021  

 https://www.tatnews.org/2021/02/provincial-entry-and-exit-rules-as-thailand-eases-covid-19-control-measures/

gives the following info for Ubon Rat: 

Ubon Ratchathani: All visitors must show official documents to prove their travel was necessary. They are also required to register with the Hug Ubon contact tracing application and take DMHTT precautions.  
Visitors from Ang Thong, Bangkok, Chanthaburi, Chon Buri, Nakhon Pathom, Nonthaburi, Pathum Thani, Rayong, Samut Prakan, Samut Sakhon, and Trat are also to report to the local administration or public health office and enter a 14-day home quarantine.