My wife is looking at buying a house here in Thailand. She is Thai and is a dual citizen of both Australia and Thailand (holds both passports). Can this be a problem when buying land?

No, she is Thai. Full stop.

The law that a Thai wife with a foreign spouse could not buy land changed many years changed many years ago.

If married to a foreigner the foreign spouse might need to sign a paper that (s)he doesn't have any rights/claims to the land, but that is it.

as long as she has her thai id.card no problem,my wife has uk and thai passports.when she does build she needs her former address clarification to register.

Yes she can. My Thai wife is a dual citizen and is the proud owner of our (her) land, but I have a Usufruct on it.

I have the understanding by thai laws that the thai wife who has taken a western name is only entitled to 1 rai of land.

I have the understanding by thai laws that the thai wife who has taken a western name is only entitled to 1 rai of land.

Absolutely not true mate

I have the understanding by thai laws that the thai wife who has taken a western name is only entitled to 1 rai of land.

Bar stool talk, that.

http://www.samuiforsale.com/knowledge/land-ownership-and-thai-spouse.html

In that case it's time to start buying land in my sons name.

It seems to be common knowledge that dual citizenship (one citizenship being Thai) is legal in the Kingdom of Thailand, and many go on to say it's legal because there are no Thai laws against dual citizenship.

When confronted by a Thai immigration officer, however, who "never got the memo," how does one respond?

Is there any Thai rule, regulation, or law to support dual citizenship? If not, it's checkmate. The officer says "prove it," and you respond "you prove it first."

Confused.

Response is to politely persist and if to no avail ask to speak to a superior.

http://www.samuiforsale.com/knowledge/land-ownership-and-thai-spouse.html

This my be the law, but it is often ignored. When buying a house, it was very obvious to all that I (a foreigner) was supplying the money, regardless of what the documents say.

This law is arcane - obsolete and the primary reason Thailand has fallen behind Singapore as the leading country of South East Asia. When Singapore separated from Malaysia, they began allowing foreigners to invest, buy houses, etc., and immediately began climbing from the poorest nation to the wealthiest.

There is nothing wrong with giving your spouse money, including for buying land.

What is not allowed is that a Thai national buys it as a front for a foreigner. That is a whole different thing and much harder to proof.

I have the understanding by thai laws that the thai wife who has taken a western name is only entitled to 1 rai of land.

Bar stool talk, that.

http://www.samuiforsale.com/knowledge/land-ownership-and-thai-spouse.html

Do not seen anything in that link that supports your original post that land can not be owned if having a western name - it can - but it can not be jointly held with a foreign spouse - it is held in the Thai citizen name only (regardless of what that name may be) and to buy the money must belong to the Thai citizen.