Separate the island parks from Phang Nga Bay
The Similan and Surin island groups are offshore national-park destinations associated with Phang Nga's Andaman coast. They are different from a Phang Nga Bay itinerary visiting limestone formations around Ko Tapu and Ko Panyi. A booking described simply as “Phang Nga islands” needs a more precise destination. Start with the named park and the activity you want: a snorkelling outing, a dive trip or time on a permitted beach. This distinction is more useful than choosing between attractive photographs that may show entirely different journeys.
For Similan, locate the actual departure pier
TAT identifies Thap Lamu in Phang Nga as a departure point for reaching Mu Ko Similan. If you are starting in Phuket, ask whether the offer includes a road transfer to that pier or uses another departure arrangement. Then add the sea journey to the road journey before deciding how demanding the day will be. Ask where the trip ends and what happens to the return transfer if plans change. A tour sold in Phuket does not necessarily depart from a Phuket pier, and the pickup time matters as much as the headline activity.
For Surin, compare the complete format
Treat a Surin outing as its own proposal, with its own embarkation point and programme. Ask for a written breakdown of the transfer, time on the water, planned stops and meals. If you are comparing it with Similan, use the same questions for both rather than assuming they differ only in scenery. Clarify whether the main activity is guided snorkelling or diving, what equipment is supplied and what experience the operator expects. Do not book a more demanding format simply because an itinerary uses the word “beginner” without explaining what participation involves.
Check park access before building the holiday around it
National-park access and permitted activities can change, so verify the current park announcement and the operator's arrangements for your travel dates. Older pages describing camping, bungalow stays or seasonal opening patterns are not current booking information. Ask which stops are actually permitted, which are conditional and what the cancellation terms cover. Read current marine forecasts close to departure. For a short Phuket trip, one offshore expedition can occupy a substantial share of the usable time; compare it honestly with an on-island coast day or a more flexible week-long plan before deciding.