I am an American living in Chiang Mai on a retirement visa. I am currently in Kunming but I am returning to Thailand and want to take my Chinese GF to stay with me on a tourist visa. We want to go overland by bus, 1st visiting some places in China before crossing Laos, and finally crossing Thailand via Chiang Kong. I also plan to return to China with her after exhausting her tourist visa + extensions by bus as well. I get conflicting information from the Thai consulate sources. The Kunming Thai Consulate website says (1) the visa is up to 60 days (2) one must have a round trip air ticket. At the Thai consulate, the clerk showed me a document with visa info, saying (1) the visa is upto 1 month (2) I need a roundtrip or return ticket (don't remember which) by air, boat or bus.
Does anyone have any past experiencing getting a Chinese National into Thailand without flying?

Not sure about arriving overland for Chinese nationals, but I know that Chinese nationals can get a 15-day on arrival visa for 1000 Baht at airports only I believe. Therefore, it may be necessary to get a 60-day tourist visa from the consulate in Kunming if your girlfriend wants to stay longer than 15 days since those visas are non-extendable I believe. I don't think it is really necessary to produce a return or round-trip air ticket but each consulate has its own rules, and for Chinese nationals they will probably enforce such rules more rigorously than for other foreigners.

A return bus ticket is probably not of much use, as I never heard of this being accepted or even heard of anyone purchasing a cross-border return bus ticket, I think it has to be a plane ticket - but do check to confirm.

China Eastern has 3 weekly flights from Kunming to Chiang Mai. Otherwise, Thai flies 5 times weekly from Kunming to Bangkok with connections to Chiang Mai.

The Thai ministry of foreign affairs website should be able to tell you whether or not a 15-day visa can be granted on arrival at land crossings for Chinese nationals, however, also remember that your girlfriend will probably need a visa to enter Laos and this may need to be arranged in advance for her, but not for most other nationalities as a visa-on-arrival is available for Americans, other western nationals and most ASEAN member states get a free one month permission to stay in Laos.