The east coast of Malaysia is in best weather in August, it also has better beaches, IMO, than the west coast. The the most beautiful beach in Malaysia (and possibly all of South East Asia) is, IMO, Rawa Island, on the east coast off Mersing. It is a small island (you can swim or canoe around it). It is without doubt one of the most beautiful beaches in the world: soft white sand and clear water that changes from blue, to green to purple depending on weather. There is one hotel on the island, and as it is small, the staff is very attentive. The hotel is about a 3-star, but the beach and surrounding islands make up for any lack of luxury. The diving is great, you can dive or snorkel right from the beach, or the hotel will arrange for a boat to take you to more remote islands/reefs/wrecks. For the hotel, see http://www.rawasfr.com/. There is a more budget bungalow hotel next door called le club rawa, take a look at http://www.journeymalaysia.com/islandrawaleclub.htm. To reach Rawa, you can take a bus or hire taxi from Singapore (3 hours) and then take a ferry for about 1 hour. It would also be possible to go overland from Kuala Lumpur, I think you would find express buses going to Mersing via perhaps Kunatan or Kota Baru. This would be a longer trip.

If you haven't already seen it, a good website is http://www.geographia.com/malaysia/
islands in the Malay archipelago. Some of the islands allow camping, I would check websites or the Lonely Planet guide for details on camping.

Some other suggestions would be:

--Pulau Sibu/Pulau Tinggi - There are several islands in the Johor State including some marine parks. (Rawa is a bit north of these.) Take a look at http://www.paradises-ink.com/asia.members/Malaysia/johor.cfm and http://amranns.tripod.com/JohorRecreation.htm for suggestions on islands. A helpful commercial site for Sibu is http://www.siburesort.com.

--I am not a fan of Tioman Island, but if you stay on Tioman, avoid the larger resorts and go to the north and other less-developed parts of the island. The Lonely Planet guidebook would probably be a good source for less-touristed hotels. Tioman is principally a weekend place for Singaporeans on a budget and really IMO is not a nice beach, or a good snorkeling (or diving) location. (I used to live in Singapore.) I would not recommend Kuantan as there is not really any snorkeling from the beach nor any nearby islands to go to for snorkeling.

--Perhentian Islands. People seem to use the term “Perhentian Islands” to refer to several different islands in diverse locations in the South China Sea. I have always thought of the island of Redang and its neighboring islands off the coast of Kota Baru and Kuala Terrenganu (including Pulau Perhentian), as being part of the Perhentian islands. Redang is a very lovely island with several hotels, and may also allow camping. From Singapore or KL, you can fly or take a bus to Kota Baru and take a ferry over to Redang or the other islands. You can also fly dierctly to Redang Island from Singapore or KL on Berhaya Air. Without knowing your budget, its hard to recco hotels, but you could look at the The Redang Beach Resort (http://www.berjayaresorts.com.my/redang-beach.). Tow other hotels which I have seen but not been insidare the Coral and the Laguna. Otherwise, take a look at at http://www.perhentian.com.my/

--If budget permits, rent a car (or motocycle!) either in Singapore, Kuala Lumpur, Johor Bahru (just over the boder from Singapore and usually a cheaper place to rent cars) or somewhere on the east coast and drive up or down the coast. The road winds through rubber and palm oil plantations. There are lots of beautiful deserted beaches and small villages, including the lovely little fishing towns of Marang and Rantu Abang. You can hire fishing boats to take you out to deserted islands for snorkelling, etcs. If you are very lucky, you may be able to see the giant leatherback turtles which come to lay eggs along the north part of the coast in July and August. There is a wonderful 5 star hotel near Kuala Terrenganu, the Tanjong Jara, that is one of my favourite places. Take a look at Take a look at http://www.tanjongjararesort.com or the website for Small Luxury Hotels of the World at: slh.com (might be a bit far for a weekend drive).

--Koh Samui, this is in Thailand, but on the east coast and just north of the Perhatians, so would also be in good weather in August. There are tons of hotels there, so you would have to give a budget to get reccos, or try tripadvisor.com

There really aren't many good beaches in Vietnam. Phu Quoc Island is probably the best choice. Mui Ne is OK. Nha Trang is also OK.

We stayed at JapaMala resort on the northern side of Tioman Island. Snorkeling at the resort wasn't great, but a short boat ride away was some excellent snorkeling. The resort was great.

Thanks for you very informative reply, Cicerone. Good of you to take so much time over it. Also for the Vietnam input, Bisbee. i will now get in action!

Phu Quoc is an interesting place to go, Casia Cottages are quite nice and the beach is ok.But there are no t.v's used hammocks for some great r and r time.