It's shocking, though not surprising given how Thai politics work, that the government-aligned Bhumjaithai and the opposition Pheu Thai are now forming an administration. This is just the latest chapter of a troubled story; after years of criticizing its betrayer over draconian policies, Pheu Thai leaders have surrendered their reputation and principles with the aim of returning to power.
This coalition further indicates that Pheu Thai is repositioning itself on the political spectrum to become Thailand's main conservative party, possibly in response the monarchy-critical Move Forward Party's recent shift to become dominant in the left-leaning camp. This isn't about abandoning principles, but adapting to the reality that a government will not be formed without a level of compromise, and that it wouldn't be sensible to compete with Move Forward for the votes of Thailand's anti-establishment youth.