Islamic religion of the Malays. In 17th century Cambodia, a polity renowned for its Buddhism, king Ramathipadi I converted to Islam, took the name Muhammad Ibrahim, married a Malay Muslim of a princely Cham family, had his courtiers wear krisses and used Malay language in correspondence. During the same century in Champa, a once powerful Indianized polity but by that time retreating before the advancing Vietnamese, the rulers held the title Paduka Seri Sultan which is so common in the Malay polities. These rulers were in close contact with the peninsula, in particular Kelantan. French missionaries reported the presence of scribes and religious scholars from Kelantan right into the 19th century. It was believed that Kelantanese who eventually helped to give the Cham struggle against the Vietnamese, the character of a religious crusade. In Brunei Sultanate, many of the Muslim subjects of the Sultan were converts from local Dayak groups. Acculturation had also taken place in Sarawak and Northern Borneo (modern day Sabah), where Brunei Sultanate and by the 18th century the Sulu Sultanate were collecting products for China and other markets, and establishing a fairly loose, river based governmental presence. Dayak chiefs were incorporated into the Brunei hierarchy, being given Malay titles such as Datuk, Temenggong and Orang Kaya. What had once been independent villages were gradually built into wider units, and their leaders co-opted into the hierarchy of the polity. A colonial writing about Sarawak, observed that many non-Malays would be amazed to learn the degree to which the present Malay population derives from the local native sources, and among the latter are Sea (Iban) and Land Dayaks (Bidayuh). In northeastern Borneo, the Bulungan Malays appear to be of Kayan origin. Further down the east coast, the Paser polity had extended its influence into the Barito-speaking Dayak, and some of these people became Muslim and were eventually referred to as 'Paser Malays'. In southern Borneo, the Malay-speaking Sultanate of Banjar had been pushing inland since the 17th century, bringing Dayaks into its Muslim culture. In the west, the development of such sultanates of Sambas, Sukadana and Landak tells a similar tale of recruitment among Dayak people. An examination of the spread of the Malay culture should not neglect the Philippines, where things may have developed differently only because of the Spanish Conquest. The influence of the Brunei sultanate in the Luzon region before Spanish rule is well recorded.