I have been to all of the Thai moto gp rounds and it’s a fantastic experience,everyone so friendly ,no price hiking with beer and food allowed and never bought tickets from rip off companies,I go early Friday morning of race weekend and buy tickets on site at ticket office at entrance to the circuit,always for main grandstand where you can see 95 % of circuit 5000 Thai baht for Friday Saturday Sunday which works out around 100 quid,try that at silverstone
this is true in my case on several occasions, the airline will not let you onto the aeroplane if you do not have the required proof of onward or a return ticket within the Visa on entry validity date and that does not include any extra days you get from immigration (ie 30 days )when you are in Thailand.this was my experience and I believe it still is is the case