I was told there is a packaging/boxing service at the airport. I am not talking about the plastic wrapping, which some airlines consider insufficient. plan B would be to get it boxed at a bicycle shop ,and take a taxi to the airport. where would be the bicycle shop nearest to the airport?

Always try the forum search window first. This subject came up on another thread a few years ago   : https://aseannow.com/topic/1022585-wrapping-a-bicycle/     .

There was a recommendation for   velothailand.  Prices may have changed since Jan 2018.

@ChouDoufu:

"velothailand will box your bike for 250 baht

including materials."

 

Velo Thailand

https://bicyclethailand.com/velo-thailand-bicycle-touring-company/

 

 

 

 

 

There's also a do it yourself video here in case you're stuck somewhere without any other options.

 

 

1 hour ago, Seth1a2a said:

Prices may have changed since Jan 2018.

 

Only slightly. https://www.velothailand.com/service/