@Maksym **********
that's wrong. Usually, many people, including you, are confusing the visa validity with the duration of the stay permit you will receive upon entering Thailand based on a visa
a Thai visa is VALID for use for an entry, for 90 days, beginning on the date of its issue
If you enter Thailand within this validity period, you will be stamped in for a 90-days stay permit. A single-entry visa will EXPIRE / become INVALID when you enter