Thailand could follow the stronger coalition

Could Thailand join the Allies without the same Japanese pressure and the 1941 Franco-Thai War?

Potentially. Phibun Songkhram was a political survivor willing to follow the side that offered the safer course.

Thailand's alignment depends on circumstances. Without the same route through the Franco-Thai War and Japanese pressure, an Allied choice becomes plausible. Phibun's ability to adjust to changing circumstances makes the balance of power around Thailand central to the decision.