Whether you take travellers' cheques, cash or cards is a personal preference.
I couldn't be bothered with the inconvenience of travellers' cheques - If I'm out shopping and don't have enough cash, I either use visa card at store or hotel or just go to ATM - they are everywhere so no real problem with that option.
I don't want to alarm people but the scams that you refer to don't just apply to credit cards......... they apply to debit cards used at ATMs through card-reading devices attached to ATM machines - you'd never know they were there but they read your card details and also your PIN and criminals can then charge stuff to your card or make copies.
People don't realise it's happened until a) they can't get their card back out of the machine (but that usually tips the customer off to something being wrong and then they can take action ) or b) the more sinister method.... you can get your card back but don't realise it's been skimmed until you or your bank start seeing transactions from countries where you've never even been.
A friend of mine had his bank call his employer to verify if he was in Paris as large amounts were being spent on his card.... he wasn't there at the time. His card may have been skimmed in Thailand, Spain or even Australia - he had no idea where or how.

In about 30 trips to Thailand I've never had money stolen or had a problem with any of my cards (credit or debit).
I always use ATMs in 'secure' areas - within shopping centres or BTS - these areas are very busy and security guards are around while these places are operating, so no chance for scammers to instal spyware on the ATM. That's my theory anyway.
ATMs on quiet side streets could be fiddled with late at night and nobody would see this being done, so best to avoid these.

I see you're Australian and ask about credit union cards.
I have a credit card from a credit union - no problem with this anywhere in Thailand.
It doesn't have a PLUS or Cirrus label anywhere on it, but has a silver logo on front with a bird on it. The debit card from the same credit union has no PLUS or Cirrus label - just VISA on the front and a silver strip on the back. I can use this card at some ATMs but not others.
My credit union charges me a foreign currency fee as well as a fee for using an ATM that isn't linked to them so these fees add up if you make frequent ATM withdrawals.

Take the advice of others and withdraw larger amounts. If you're worried about bag snatchers, keep your $$ in a bumbag or one of those bags that has a string for around your neck and you can wear the bag under your shirt.