Regional religious practices in Southeast Asia significantly altered Vishnu's attributes and symbolism by integrating local beliefs, religious syncretism, and political contexts that adapted his traditional Indian characteristics to new cultural landscapes.

1. Integration with Local Deities and Cosmology

• In regions like Sri Lanka, Thailand, and Cambodia, Vishnu was often merged or identified with indigenous and Buddhist guardian deities. For example, in Sri Lanka, Vishnu became known as Upulvan, a protector of Buddhism and the island, blending Hindu and Buddhist elements.

• This synthesis broadened Vishnu's role from solely the Hindu preserver god to a more universal protector figure, revered in multi-religious contexts.

2. Modification of Iconography and Attributes

• Vishnu’s quintessential blue skin, symbolizing the infinite and the cosmic ocean, was retained but sometimes adapted to local artistic styles, varying hues to align with regional symbolic representations.

• The traditional four attributes—conch (shankha), discus (chakra), mace (gada), and lotus (padma)—remained, but their artistic depiction changed to reflect local aesthetic norms. In Khmer and Javanese art, for instance, Vishnu’s attire, posture, and facial features were localized to suit regional tastes and spiritual expressions.

• Unique forms emerged such as the horse-headed Vishnu (Hayagriva) in Khmer art, reflecting indigenous mythologies fused with Hindu symbolism.

3. Emphasis on Kingship and Divine Authority

• Southeast Asian kingship adopted Vishnu’s symbolism to assert divine right and cosmic order. This transformed Vishnu into a symbol of political legitimacy and earthly sovereignty, linking rulers directly with the deity.

• His avatars, particularly Rama and Krishna, were also emphasized in local traditions to exemplify righteousness and ideal kingship, often reflected in local literature, dance, and temple reliefs.

4. Syncretism with Buddhism

• In Theravada Buddhist Southeast Asia, Vishnu was revered not just as a Hindu god but also as a protector of Buddhism. This role shifted Vishnu’s symbolism toward guardianship and religious custodianship.

• His worship was integrated into Buddhist practices, with shrines dedicated to Vishnu found within Buddhist temple complexes, especially in Thailand and Sri Lanka.

5. Transformation in Worship and Ritual

• Vishnu’s worship adapted to local rituals and festivals, often blending with indigenous and Buddhist ceremonies. This resulted in a more communal and culturally embedded form of veneration where Vishnu’s cosmic preservation role was linked with local notions of prosperity, protection, and social harmony.

Summary

Regional religious practices in Southeast Asia expanded Vishnu’s attributes and symbolism from a strict Hindu theological framework to a more inclusive and localized spiritual figure.

He became a guardian deity of Buddhism, a divine legitimizer of kingship, and an icon whose visual representations incorporated local artistic and mythological themes. 

These alterations allowed Vishnu’s worship to flourish in diverse cultural milieus while preserving his core identity as preserver and protector.