if they question you then you should have 20k baht on you, flight out of Thailand within the visa/exempt period, and proof of accommodation. Even then it doesn't guarantee you entry.
yes but in 2020 and during Covid so things might be different now.
My wife had same extension of stay as your wife and I was working and had extension of stay based on employment. My wife's future employer liaised with my employer at the time in order to get everything that was needed and ensured that my wife's extension of stay wasn't cancelled until they had all of the paperwork in place.
Note as travel overseas was very difficult in Q2/Q3 2020 this was all done within Thailand, including her getting herself sorted so she could work legally in Thailand.