The plant below with red flowers was seen in the Singapore Botanical Gardens with the label "Dasymaschalon blumei" on it. Since Dasymaschalon blumei is a synonym of Dasymaschalon dasymaschalum according to the Plant List website, I had assumed that it is the same species as the one above found in the wild.

The identity of this plant is not conclusive. In the publication by Wang et. al. [1], there was a picture of the fruit of Dasymaschalon dasymaschalum (page 547) which was more elongated than the one seen in the above picture. In another publication by the same author 3 years later [2], the same picture was labelled as Dasymaschalon glaucum. There was a picture of the flower and fruit in the later article (pages 255 and 259) which resembled the yellow-flower version above.

Publications:

[1] Wang J, Chalermglin P, Saunders RMK. The genus Dasymaschalon (Annonaceae) in Thailand. Syst Bot 2000;34:252-265. | Read abstract |

[2] Wang J, Thomas DC, Su YCF, Meinke S, Chatrou LW, Saunders RMK. 2012. A plastid DNA phylogeny of Dasymaschalon (Annonaceae) and allied genera: Evidence for generic non-monophyly and the parallel evolutionary loss of inner petals. Taxon 2012;545-558. | Read abstract |