The top word is piset - พิเศษ - meaning "special." Underneath is the initial for "weight," น., 15, and the initial for baht-weight, บ. The Thai baht is the country's unit of money, but in the past "baht" was also used as a unit of weight for approximately 15 grams, or half an ounce. So it means 15 baht-weight, which would be about 7.5 ounces. (There is no maker's mark present.)
"Piset" (special) is one of about four designations for high grade Thai silver (There’s also “Good,” “Special,” “No. 1,” and “Pure Silver.” Unfortunately, all four are used rather loosely, but should indicate at least 90 percent silver.
However, in my collecting of Thai silver objects (mostly bowls), I have discovered a LOT of cheating, including on old pieces. So, while your piece indicates silver in the range of perhaps 92.5% - 95%, it may be made of a much lower grade of silver, or even various alloys of tin and/or nickel silver. Some of my fakes are quite convincing in color, patina, and feel. So, you need to test it for silver content. And be sure to test both the bottom and the sides, as they could be of differing alloys. I have examples of that.