Can I extend my 30-day entry permit in Thailand and what do I need?

Just getting info clear. Am here on whatever the 30 day entry permit is called. (Was out of the country once to renew.) Am I right that I can go somewhere and get a 30 extension for 1,900 Baht? And if so, where do I go? And do I need anything besides my passport - and the Baht. 20,000 Baht? Thank you! (Plan is to be here until mid November and working options.)