I have two british passports and do this all the time. You can use both at check in, explain this is one for visa of country you are going to and this is one with my Thai visa. At immigration only show the one you entered country on.
(Sometimes they want to check valid Thai stamps at check in. Not often but sometimes)
Phuket yachts and marine. Not normally one to critise spelling as dsylexia is quite common in our family. But would think a dealer of Yachts would at least know that one.