Learn Hardcore Swedish: Kommer kunden med buss eller tåg? - Is the customer coming by bus or by train?

Yes. Swedish often uses the present for near or scheduled future. Kommer kunden …? naturally means “Is the customer going to come…?”
Alternatives and nuance:

Ska kunden komma …? plan/intention.
Kommer kunden att komma …? neutral prediction.
All three are correct; style and nuance decide which you choose.

Why is it kunden and not kund?

Swedish marks definiteness with a suffix. kund = “a customer,” kunden = “the customer.”
Use kunden when a specific, known customer is meant. If you mean any customer, say: Kommer en kund med buss eller tåg?

Why is there no article before buss or tåg?

With means of transport, Swedish normally uses the bare singular after med: med buss, med tåg, med bil, med cykel, med taxi.
Using the definite form refers to a particular vehicle: med bussen / med tåget (e.g., the 8:15 bus, that specific train).

Is med the only correct preposition for transport? What about på or i?

Use med to express the means (“by”): Kommer kunden med tåg?
Use på or i to express location on/in a vehicle:
- på for public/shared vehicles: på bussen/tåget/planet (on the bus/train/plane).
- i for enclosed smaller vehicles: i bilen/taxin (in the car/taxi).
  So: Kommer kunden med buss? but Är kunden på bussen?

Can I drop med and just say something like “Kommer kunden buss?”?

Not with komma. With komma, you need med to introduce the means: Kommer kunden med buss …?
However, with åka (to travel), you can drop med: Åker kunden buss eller tåg?

What’s the difference between kommer (med …), åker, and tar?

Kommer (med …) focuses on arrival: “come/arrive (by …).”
Åker (buss/tåg) focuses on traveling by that mode: “travel/go by bus/train.”
Tar (bussen/tåget) means “take the bus/train,” usually with the definite form because you’re choosing that mode (often a specific service): Tar kunden bussen eller tåget?

Should I repeat med before tåg?

Both are fine:

… med buss eller tåg (most common with short items)
… med buss eller med tåg (repetition can add clarity, especially with longer phrases).
No difference in meaning here.

How do I negate this question?

Neutral placement (adverb after the subject): Kommer kunden inte med buss?
Emphasis/surprise on the subject: Kommer inte kunden med buss?
Both are grammatical; the second often implies you expected the opposite.

Where do time/place words go in this question?

Keep the verb first, the subject second. A common order for adverbials is time → manner/means → place. Examples:

Kommer kunden i morgon med tåg?
Kommer kunden i morgon med tåg från Göteborg?
Kommer kunden vanligtvis med buss?
There’s flexibility, but avoid breaking the initial verb–subject order in yes/no questions.

Can I say Är kunden med buss?

No. är … med doesn’t express means of transport.
Use:

Kommer kunden med buss? (means “by bus”)
Är kunden på bussen? (location: “on the bus”)

Pronunciation tips for tricky sounds here?

kommer: the first vowel like English “o” in “cot” (not “cone”); double mm gives a long m.
kunden: Swedish u is a fronted vowel (between English “oo” and “uh”); the d is pronounced.
med: often pronounced without a strong final d in casual speech (“me”).
buss: short vowel + long ss (hiss-like).
tåg: å is a long, rounded vowel (like “aw” in “law” but rounder); the g is pronounced.

Does this ask about a specific trip, or could it be about the customer’s habit?

Both are possible. Swedish present can be specific (“for this arrival”) or habitual (“usually”). Context or a time word disambiguates:

Specific: Kommer kunden i dag med buss eller tåg?
Habitual: Kommer kunden (vanligtvis) med buss eller tåg?

How do the plural forms work for buss and tåg?

buss (common gender): singular en buss, plural bussar, definite singular bussen, definite plural bussarna.
tåg (neuter, zero plural): singular ett tåg, plural (flera) tåg, definite singular tåget, definite plural tågen.
In the transport-meaning expression you still use the bare singular: med buss / med tåg.