Just posting this from a Lop Buri website on "how to get here"
From Bangkok: The trip from Bangkok to Lop Buri by car may take up to 2 hours. It is possible to either drive along Highway No.1 via Saraburi (total distance is 153 kilometers), or use Highway No. 32 via Ayutthaya, and travel further along Highway No. 347 to Lop Buri via Tha Ruea District.
From Bangkok: Air-conditioned coaches and non air-conditioned buses leave Bangkok's Northern Bus Terminal (Mo Chit 2 Bus Terminal) every 20 minutes from 5.30 a.m. until 8.30 p.m. The ticket costs 62 baht (ordinary bus) and 85 bahts (air-conditioned). The journey takes 3 hours. Call 02 936 2852-66 for more information.
From Bangkok: Ordinary northern-route (Bangkok-Chiang Mai) trains leave Bangkok's Hua Lamphong Railway Station at 7.05 a.m. and 8.30 a.m. Both are third class only. Rapid trains leave the station 5 times a day (Travel time is 2.5 hrs.) For more updated schedules and reservations, call 1690, 0 2223 7010, 0 22237020 or visit www.railway.co.th