Not an expert on chemistry here, so if a better answer appears, I'm happy to defer, but I would assume this refers to salts in the chemical sense, meaning an ionic compound.

According to Wikipedia: "Salts are often referred to only by the name of the cation (e.g., sodium salt or ammonium salt) or by the name of the anion (e.g., chloride salt or acetate salt)." Or from the Thai wikipedia: "เกลือมักถูกกล่าวถึงโดยชื่อของแคทไอออนเพียงอย่างเดียว (เช่น เกลือโซเดียม หรือ เกลือแอมโมเนียม) หรือเรียกโดยชื่อของแอนไอออน (เช่น เกลือคลอไรด์ หรือ เกลืออะซิเตต)"

Because the scientific terms are identical in both language (salt/เกลือ), given the context, and because there is very little on the internet about this term other than the boilerplate text I assume you're translating, I would assume that เกลือของเภสัชเคมีภัณฑ์ just refers to any ionic compounds that could be used as pharmaceutical chemicals or are derived from pharmaceutical chemicals. The fact that practically every webpage has the same boilerplate text might suggest that it might be more of a catch-all term used in this specific legal document to encompass a lot of possible chemicals, but not one that is used often in chemistry because it is rather vague.