We did it when we first moved here, and I, like you Big Boy don't trust lawyers in general, especially those who set up shop and call themselves a lawyer when they are really just a paralegal like many here in Hua Hin. (and most politicians in the U.S. were lawyers before they went into politics

)
For peace of mind we had both of ours drawn up by a big very professional law firm in Bangkok. I think it cost around 10k baht, but I feel it was done legally and correctly so for me it was worth it. The main point then was the big house and land we owned in my wife's name. Should something have happened to her before me, that would have gone to her relatives and I could have been tossed out on my ass with nothing. Our
will stipulated that in the case I outlived her I had control of the property for life including the freedom to sell it and keep the money or live in it for the rest of my life. Another longtime expat here pointed me to the law firm as he had done the same thing and his wife did pass away before him about 9 years ago. He continued to live in the home after going through probate court (because of the
will) until very recently when he sold it. Had he not had that
will his wife's relatives could have (and probably would have) tossed him out onto the street immediately.
If you own your home, make sure it covers this possibility as well as who
will inherit your possessions should both of you pass at the same time.
Also, if you have any assets in the U.K. or if what happens to your pension would be questionable. You need wills there too. The
Thai will only covers Thailand. We had to do two in the U.S. and two in Thailand.
We used these people for our
Thai wills... very professional large law firm. It was a while ago so if you decide to use them call ahead for the current cost.
http://www.pensitandlaws.com/about_us.html