The Spanish colonization of the Philippines was always intended for the purpose of accessing Asian markets for spices and silk. It also started because it was regarded as naturally within the Spanish sphere of influence, as determined by the Treaty of Tordesillas in 1493, since it was believed the Philippines were on the Spanish side of the line in the Pacific.

It is important to note that Spanish expansion of the 16th century did not necessarily follow strictly commercial interests. Rather, it was a combined military and religious endeavor, that both seeked to expand Spanish power as wide as possible, and to facilitate the spread of Catholicism, which became extra important in light of the Reformation.

The real impetus for the colonization of the Philippines came with hte discovery of the Urdaneta Route, that allowed ships to sail back across the Pacific with relative east, and not just west. This enabled the Spanish to sail American silver straight to Manila to buy spices and especially Chinese silk.

However, the Philippines were also intended as a springboard for further conquests. In the first century after the foundation of Manila in 1571, several expeditions were launched. The Spanish attempted an invasion of Borneo, and military interventions in Siam and Cambodja, driven largely by private adventurers. At one point they even planned to use the Philippines as a staging point in the conquest of China, and some briefly considered invading Japan.

This shows that the cultural experience of the Spanish largely shaped their expansion in Asia. Unlike the Portuguese, whose culture of colonization became crafted around dealing with Asian rulers whose power was largely on parity with the Europeans, the Spanish came with their American experience of military superiority, and therefore their early arrival in the Philippines had the same mentality of expansion that their American experiences were shaped by.

Ultimately, these attempts at expansion came to naught. The invasions of China and Japan were quickly scrapped, and the interventions in Southeast Asia never managed to gain a foothold. The only other two somewhat lasting Spanish possessions in Asia was the forts in Tidore, founded in 1606 to counterbalance the Dutch. These were abandoned in 1662. The other was the short-lived colony on Formosa, Taiwan, founded in 1626, and lost to the Dutch in war in 1642. These were thus both meant to balance the Dutch. By the early 17th century, Spanish power was waning globally, and the policy of expansion was being put on hold over much of the world. Madrid didn't really sanction resources for further establishment of colonies, preferring to hold onto what they had.

So the answer to your question is that Spanish policy in Asia was one of expansion, due to their experience in America, at least for the first decades of Spanish rule. Although Manila ended up being mainly an entrepot for Asian trade, originally it was intended to also be a launching pad for military conquests of the Asian mainland, and of the Catholic missions in Asia. In the same way the Caribbean islands had been the launching pad for the conquest of mainland America. As this failed - indeed, the Spanish even failed to conquer all of the Philippines, as fights with the Muslim Moro people lasted until 1898 - Manila instead ended up mainly as a waypoint to the riches of China. But this was not the way it was intended originally, but merely the result of enterprises in the mainland failing.

I hope that answers your question. My main source for this is The Spanish Experience in Taiwan, 1626-1642 by José Eugenio Borao.