Getting there
It is a little bit of an effort to get to Phanom Rung, but well worth it. If possible avoid weekends when the whole area is packed with local tourists and the scene is often not particularly conducive to a quiet appreciation of the site.
During the festival in April it is packed solid (but the festival is worth seeing). Early morning (before 10:00) offers the best light for photography.
Phanom Rung can be approached from Khorat, Buriram, Surin or nearby Nang Rong. From Khorat, Buriram or Surin catch a bus to Tapek which is 11 kilometres to the east of Ban Ta Ko. It is well signposted as the turn-off to Phanom Rung. Get off the bus there and wait for a songthaew which runs to the foot of the hill.
The songthaews can be quite infrequent (especially on weekdays) so if your patience gets the better of you, catch a motorcycle straight to the ruins and organise for them to wait for you while you visit the site - do not pay up front! If you get a songthaew to the foot of the hill you can then get a motorbike taxi up and back. On weekends, songthaews are far more regular.
If you come from Nang Rong, catch a songthaew straight to the foot of the hill. These leave from the market, most are clearly marked as running to Phanom Rung. Once at the bottom of the hill you will have to catch another songthaew or motorbike to the top.