One of the things to see if you spend time in Ranong are the Hot Springs.
Just east of the city they are well signposted.
The area around the Hot Springs is, predictably enough, lightly developed with thai business catering to food and refreshment along with souvenirs.
If you bear right as you reach the Hot Springs junction you'll find the main bulk of the springs up there. As we aren't the tourist type we won't spoil you with the pictures of them. You'll have to go see them for yourself. To whet your appetite here's a lesser spring hole, next to the Police Depot nearby.
Getting to Ranong Hot Springs
Follow Petchkasem road south from the outskirts of northern Ranong. The signs for 'Hot Springs' will start appearing on your left. You'll pass a 'spa' hotel and a derelict kareoke complex. You need to take the next left (just after the 7-11). This road (pictured at the top) will lead all the way to the hot springs. MIND THE SPEEDBUMPS!
Being about 420 km from Bangkok means about 4.5 to 7 hours drive time. A distant airport operates flights out of the city but this is usually on an infrequent basis.