The problem with most of the Chinese lasers is they are cheap for reason. If you buy a coherent version of whatever it is you have you will not have these issues.
It all boils down to, you get what you pay for. I would've killed to have what we can get now for practically nothing, 25 years ago. When I started, 7 mW Of 632.8. HeNe Was 800 bucks. Now we can get 200 mW of 650 courtesy of Pioneer for $30. the biggest problem I've seen with the Chinese stuff are the DPSS blue. they have an absolutely terrible beam intensity stabilization. They are getting a little better but still vary in intensity and depending on a number of factors if you look really carefully.
As to your question. You're on the right track. Try and keep things as thermally stable as possible. I have seen Chinese DPSs's with cardboard tubes for optics mounts. Not surprisingly, they are susceptible to differences in humidity and temperature, and the alignment of the planets and the particular voodoo, You do, so well...
You can try and TEC cool it, but I'm sure there are a dozen other variables that are conspiring to work against you. Just be glad you can ge t140 mW for the price should can and trying keep things as cool as possible.
chad
When the going gets weird, the weird turn pro.