Tilman Frasch on the Singhalese raid on Lower Burma around 1164-5

Frasch, Tilman (2002) “Coastal peripheries during the Pagan period,” In The Maritime of Burma: Exploring Political, Cultural and Commercial Interaction in the Indian Ocean World, 1200-1800, Edited by Jos Gommans and Jacques Leider, Leiden: Koninklijke Nederlandse Akademie van Wetenschappen, pp. 59-78.

Luckily I have this paper by Tilman Frasch that seems to clear up a lot of the confusion in Aung-Thwin's rambling 1976 paper:

...the Singhalese raid on Lower Burma around 1164-5 which King Parakkama Bahu I of Polonnaruva had sent to extract revenge for insults he had suffered at the hands of the Burmese. According to the contemporary Sinhalese chronicle Culavamsa [9], the Sinhalese forces captured the two port towns of Kusumiya (Bassein) and Muttuma (Martaban) as well as a third place called Ukkama which may be identified as Okkam, a place some twenty miles north of Rangoon [10]"

[9] Geiger 1925/1929, ch. 76.10-75. This part of the chronicle, dealing with the life of Parakkama Bahu, was written during the later part of the king's reign or shortly afterwards, and is generally regarded as highly reliable, see Geiger 1930, 205-228. The conquest of the port town of Kusumiya (Bassein) is mentioned in the Devanagala Rock inscription that records the reward King Parakkama gave to his victorious general Kit Sri Nuvaragal: Epigraphia Zeylanica 3, 312-325.

[10] I have dealt with the Sinhalese expedition and its implications exhaustively in Frasch 1998a. For earlier views, see Luce 1965a, and Aung-Thwin 1976.

References:

1. Aung-Thwin (1976) "The Problem of Ceylonese-Burmese Relations in the 12th Century and the question of an Inter-regnum at Pagan," Journal of the Siam Society, 64(1): 53-74.
2. Epigraphia Zeylanica
3. Geiger (1925/1929) The Culavamsa. Being the More Recent Part of the Mahavamsa, London: Pali Text Society.
4. Geiger (1930) "The Trustworthiness of the Mahavamsa," Indian Historical Quarterly, 6 (2): 205-228.
5. Luce (1965b) "Some Old References to the South of Burma and Ceylon," In Felicitation Volumes of Southeast Asian Studies, presented to his Highness Dhaninivat...on the Occasion of his 80th Birthday, Vol. 2, Bangkok: Siam Society.

Comments: This is a nice concise overview of what happened that can be filled in later with details from the Culavamsa and inscriptions. Aung-Thwin's 1998 Myths book republishes the 1976 paper. Wikipedia is missing this sort of information.