The Stock Exchange of Thailand (SET) will enforce 8 revised trading rules from 16 Nov 2026. Key changes: smaller price steps for stocks priced 5-50 baht, short selling limited to SET100, SET50-linked and similar liquid securities, a fee of 0.15 baht per order above 15,000 orders a day for high order-to-trade accounts, and removal of dynamic price bands and minimum resting time. Most small business owners do not trade shares directly. Only act if you hold listed shares, invest through a broker, or have a listed-company link. Full rules are at set.or.th.