A quick Google search yields this: “the tense marker [on an Irish verb] may appear either as a suffix, as an initial mutation of the stem, or as a discontinuous morpheme realized with both initial mutation and a suffix (eg mhol+f+ainn ‘I would praise’).” (McAuley ed, “The Celtic Languages” p. 67)

IE is not really my field. With that caveat, I’d like to suggest proceeding by analogy. Find languages outside IE that exhibit rich discontinuous morphology, then look for typological parallels with IE languages. Tagalog is one such non-IE language, and it also happens to be verb-initial. Is it possible that verb-initial IE languages (like Irish) have innovated instances of DM?

Yes, in fact Lao has high falling and low falling tones. There are two ways to spell words with the falling tone in Thai – for example, /na:/51 can be written หน้า (meaning ‘face’) or น่า (meaning ‘-able’ in words like น่ารัก ‘lovable’. Historically, this reflects a merger of two tone categories which remained separate in Lao. The falling tone also pops up in odd places when rendering foreign words, for example in the last syllable of ‘central’ – no idea why. As for being 'sweet', well it's kind of looping, that might qualify. A more pleasant sound to my ear than the one in Mandarin.

Off-topic, it might be interesting to compare the falling tones in Thai and Mandarin. Both are annotated as 51, but they differ in other ways, the Mandarin falling tone short and sharp, the Thai one longer and possibly with some special phonation.

@dainichi – thanks, I wasn’t aware of that. From Wikipedia, it seems that there is a regional difference – in southern varieties of German, /b/, /d/ etc are voiceless, so it’s better to talk about fortis-lenis pairs for German. Note that in the study, a single speaker provided the data for each language. Clearly there is a problem with generalizing in the German case, but that doesn’t necessarily invalidate the generalization that (at least some) Mandarin speakers voice /b/, /d/ etc at least half the time.

There’s an info box on the Pinyin Wikipedia page with suggestions and diagrams for pronouncing Mandarin fricatives/affricates. It makes no mention of voicing, but pretty clearly stresses aspiration (ji/zhi/zi are “gently released”, but qi/chi/ci are “blown away forcefully”.) These are definitely more challenging than the stops.

By the way, the yun/kun rime distinction is quite clear in Bopomofo, the non-Roman system used in the ROC. And in Gwoyeu Romatzyh, the transcription system featuring tonal spelling, kun1 would be ‘kuen’. This suggests that Yuen Ren Chao, who designed GR, knew what he was doing.

For background on Zhuang language policy in China, I’d check Katherine Kaup’s ‘Creating the Zhuang’ – there’s quite a lot in the Google books preview. Guangxi is an ‘autonomous region’ for the Zhuang, so you’d see bilingual signs there too, I believe.

If you keep going to Kunming, you could visit the Nationalities Park (mínzú cūn) to learn about the non-Han minorities of Yunnan. The Dongba pictograms of the Naxi in Lijiang are fascinating, if you get that far (from there, 2-3 hours further travel brings you to the Tibetan cultural region.) Of course, these aren’t Tai groups, but interesting nonetheless.