This morning I took my bicycle into Bangkok by Skytrain in order to explore the park at Suan Rot Fai.
Suan Rot Fai (13.812639,100.554235), or The Railway Park in English, is just one of three parks in the vicinity of Chatuchak Weekend Market. Suan Rot Fai is the largest at 150 acres. For people who love cycling it is a paradise as there is a dedicated track around the park that is about 3 kilometers long. In fact, the majority of the people at the park were on bicycles. You can rent bicycles for about 20 Baht at a row of shops near the Northern entrance to the park (13.816868903339,100.55290462433). Some even have baby seats. There is also a food market here where you can buy something for a picnic in the park. It seems to be a great place to bring families as there are play areas, a butterfly garden, swimming pool and lakes where you can rent boats.
In the nearby Chatuchak Park I also visited the railway museum (13.810982440578,100.55683137833). This is a privately run museum that is only open at the weekend until about 3 p.m. The nearest MRT station is Chatuchak and the BTS station is Mo Chit. You can take bicycles onto the BTS for free but the MRT only allows folding bikes.
The following map shows the route that I took on my bicycle around the park. There were also interconnecting tracks.