Teaching

I am thinking about going to live near Ho Chi Minh City July 2017 for approximately 6 weeks and possibly longer.  I am a teacher with 20 years experience and a master's degree. Will I be able to work while I am there in the summer? I teach primary school and speak English and French.

You won't have any problems finding work

You may be able to find work but put yourself in the shoes of a potential employer.  Would you hire someone who had the intent to leave in 6 weeks?  Teaching done right, no matter how much experience you have, requires a certain level of commitment.  I shouldn't have to say that to someone with 20 years of experience.

I was thinking more in terms of summer school or short term contract work, not starting a full time job and then leaving..maybe even tutoring? Something to make some extra money while immersing myself into the culture.

Thig is correct.

Nothing wrong with dipping your toes in the water

People prefer to see if you can swim